Noticed some wear on the block during a rebuild. The block is wore down about .020" at the cam thrust surface. The cam that came out looks fine with no sign of wear after about a 1000 miles. I am going to a hyd roller with the rebuild. Is this something that needs to be addressed? If so, what is the fix?
Cam Thrust Surface Wear
- Thread starter bkoons
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This needs to be addressed and it isnt that easy to fix since your block is worn. If you let it go it will get worse and send metal everywhere and eventually the timing chain will break
. You need to have the cam thrust milled and use a Torrington thrust bearing and steel races. The cam will need to have some material removed from it. Use bearing part # SUM-G1790. Its a SBC cam thrust kit from Summit. Current cost is $11.95. You will need to determine how much to remove from the block and then cut the cam to achieve the proper clearance. Cutting the cam is easy. Milling the block is a little difficult and may be too expensive unless the block has steel caps and a girdle and is worth saving. Or if you have a friend in a machine shop you may get away cheap. It needs to be set up in a mill with a turn table and the table needs to swing in a circle to cut the thrust surface correctly with the appropriate cutter. The clearance on the machine from cutter to base needs to be 19 inches or more or the block wont fit in the machine. In the future i will cut all cams for this bearing since it is more preventative and easy than fixing a block like yours once its worn. Yes ive had this happen to me before and it sucks. You will need to use a positive style thrust bumper with shims to get the clearance correct. You can not use the spring type since the steel race on the thrust bearing could fall out of place if the cam thrusts forward . Comp cams has such a thrust bumper for around $35. Set up the end play to .005-.010 after the cam thrust is repaired with the Torrington bearing. The cam center locates the 3 parts of the bearing after being turned in a lathe and the .005 assures the steel thrust washer cant fall out of place on forward thrust. The bearings probably have iron filings in them form the worn thrust. Id consider a thorough check of all bearing surfaces on the crank. Be sure to replace the timing chain. HTH
. You need to have the cam thrust milled and use a Torrington thrust bearing and steel races. The cam will need to have some material removed from it. Use bearing part # SUM-G1790. Its a SBC cam thrust kit from Summit. Current cost is $11.95. You will need to determine how much to remove from the block and then cut the cam to achieve the proper clearance. Cutting the cam is easy. Milling the block is a little difficult and may be too expensive unless the block has steel caps and a girdle and is worth saving. Or if you have a friend in a machine shop you may get away cheap. It needs to be set up in a mill with a turn table and the table needs to swing in a circle to cut the thrust surface correctly with the appropriate cutter. The clearance on the machine from cutter to base needs to be 19 inches or more or the block wont fit in the machine. In the future i will cut all cams for this bearing since it is more preventative and easy than fixing a block like yours once its worn. Yes ive had this happen to me before and it sucks. You will need to use a positive style thrust bumper with shims to get the clearance correct. You can not use the spring type since the steel race on the thrust bearing could fall out of place if the cam thrusts forward . Comp cams has such a thrust bumper for around $35. Set up the end play to .005-.010 after the cam thrust is repaired with the Torrington bearing. The cam center locates the 3 parts of the bearing after being turned in a lathe and the .005 assures the steel thrust washer cant fall out of place on forward thrust. The bearings probably have iron filings in them form the worn thrust. Id consider a thorough check of all bearing surfaces on the crank. Be sure to replace the timing chain. HTH
Turbo1dr
9 Sec Wanna-Be
- Joined
- May 25, 2001
- Messages
- 2,396
High volume high pressure pumps can cause thrust wear.
The engine & oil pump was stock. When I first got the car I pulled the front cover to fix some leaks and discovered the nylon timing chain missing a few teeth. Replaced that with a true roller & spring loaded button without pulling the cam (dropped the pan to clean out any fragments also). A year later I replaced the cam & this last year I pulled the motor to go through it. Crank journals were thrashed but cleaned up nice @ 10 under. Odd thing is the new cam I had in looks like new at the mating thrust face. Damage must have been done with the damaged stock pulley.
Thanks for the info and part numbers. As an alternative was wondering if there was a plain bearing like a transmision thrust washer that someone might know about.
Thanks for the info and part numbers. As an alternative was wondering if there was a plain bearing like a transmision thrust washer that someone might know about.
The cams are harder than the block and usually are nothing or .001-.002 to clean up the thrust. There are some copper washers that i have seen used in between the cam and block but only on un-worn blocks. I dont know a source though. The torrington is the best option. A transmission thrust washer is typically retained by a tab. You will have a hard time finding a nylon washer that will work. Your going to need to go with the milling procedure or go to a billet roller setup with a retention plate. Then you can have a small spot welded on the thrust or slightly below it and just true it to the flat part of the block. All you need is a triangle of contact points behind the retention plate. This would be an expensive route since the billet roller is an expensive change over.
- Joined
- May 26, 2001
- Messages
- 9,208
If you are going to install or change to a billet roller, the best set up is the same cam retainer that the stage and alum blocks use.
On a stock block, it requires 3 small holes to be drilled and tapped for retaining screws, and the cam nose machined for the retainer.
No spring button needed. Comp Cams does the needed machine work when we order the cam.
That will work great as long as there is 3 points of contact behind the plate. If the blocks thrust is worn it can simply be welded in a small spot and trued to give a 3rd contact point for the plate to sit on.I think this is what you speak of.
I dont have the part number. Try calling a vendor that sells the austempered cams or call the comp tech line. You may even want to try a mail order company. The last time i needed one i called Summit.
- Joined
- May 26, 2001
- Messages
- 9,208
Not sure what you mean by "3 points of contact"?
We have installed billet rollers in 109 blocks using this retainer w/o welding the block?
Also, we have the shim-type roller button in stock.
Not sure what you mean by "3 points of contact"?
We have installed billet rollers in 109 blocks using this retainer w/o welding the block?
Also, we have the shim-type roller button in stock.
The thrust surface on the block in the original post is worn down. The plate needs a flat surface to sit on. No welding should be necessary if the front of the block is not worn. If its worn a little you may not need to weld either. The 3 points are where the plate is pulled against the block when bolted down. He doesnt look like he can get away without a little weld his situation.
Cam Thrust
There are 2 ways that this can be approached , I have a tool that will allow
you to cut the surface on the block without a major hassle . Then you can
use a bronze washer from a SBC to take up the space. The other is our billet
rollers use a torrington bearing assembly which is larger than the worn area
and will ride over it . This is a much less cost effective way to repair . If you
are interested give me a call and I can explain in more detail the procedure.
There are 2 ways that this can be approached , I have a tool that will allow
you to cut the surface on the block without a major hassle . Then you can
use a bronze washer from a SBC to take up the space. The other is our billet
rollers use a torrington bearing assembly which is larger than the worn area
and will ride over it . This is a much less cost effective way to repair . If you
are interested give me a call and I can explain in more detail the procedure.
turbofabricator
Well-Known Member
- Joined
- Mar 7, 2004
- Messages
- 4,261
I have found that MOST aftermarket cams have a burr on the thrust face that causes problem. I always deburr the oil hole on the trust face, and have not had wear problems, since. Chech this out and you will see what I am talking about. Polish the thrust face (on the cam and oil hole) and it will save the block BEFORE it chews it up. Same with the thrust surfaces' of the crank, too. A little 1500 grit and elbow grease does wonders.
